A control unit of a disk array device is conventionally configured from package boxes of a plurality of types which are divided into modules according to function. In the case of a control unit of this type, an enclosure (hereinafter called a unit cover) for storing the package boxes is formed with a cylindrical shape and the interior of the unit cover is divided by racks (hereinafter referred to as shelves) into a plurality of spatial areas of sizes corresponding to individual package boxes and configured so that the package boxes corresponding to each of these spatial areas can be mounted from the front or rear side.
In this case, a connector of a predetermined shape is provided on the rear side of each package box. Furthermore, a backboard is provided, perpendicular to the direction of insertion of the package units, inside the unit cover, and the backboard is provided with connectors which correspond to the respective connectors of each package box.
Accordingly, the control unit is designed so that, by inserting each package box into the unit cover, the connectors of the package boxes can be mated with the corresponding connectors of the backboard and so that each of the package boxes can be physically and electrically connected to the backboard.